A variety of devices are compliant with Plug and Play. The following sections describe the types of devices and provide details for Plug and Play.

USB Devices

Universal Serial Bus is a bus standard that brings Plug and Play capability to external hardware devices, such as keyboards, mouse devices, speakers, and cameras. USB devices are hot pluggable , meaning that they can be connected even when the computer is running. USB devices are automatically configured when they are attached — without the need to restart the computer or run Setup.

IEEE 1394 Devices

The IEEE 1394 bus is designed for high-bandwidth devices such as digital camcorders, cameras, and videodisc players. Windows 2000 Professional supports hot plugging of IEEE 1394 devices. To use an IEEE 1394 device, obtain the appropriate Win 32 Driver Model (WDM) driver.

For more information about USB and the IEEE 1394 bus, see Hardware Support in this book.

SCSI Devices

Small computer system interface (SCSI) is a multiple-device chained interface used for many devices such as hard disks and CD-ROM drives. Plug and Play SCSI devices support dynamic changes to the adapter and automatic configuration of device ID and termination, as long as the driver supports it.

Configuration of a SCSI device can be separated into two distinct processes:

• Configuring the SCSI bus itself, for example, by terminating both ends of the SCSI bus and setting device IDs.

• Configuring the SCSI host adapter, for example, by assigning an interrupt request (IRQ) channel, direct memory access (DMA) channel, and so on.

PC Card Devices and CardBus

Products designed for the PC Card standard include multifunction cards, 3.3-V cards, and 32-bit PC Cards (CardBus). These advances add the modularity and bus-independence of Plug and Play without affecting device drivers.

Windows 2000 Professional also supports CardBus, a 32-bit implementation of PC Card also known as PC Card 32. CardBus brings 32-bit performance and the benefits of the PCI bus to the PC Card format. CardBus allows portable computers to run high-bandwidth applications such as Video Capture. For more information about how Windows 2000 Professional supports Video Capture, see Hardware Support in this book.

VL Devices

The Video Electronics Standards Association (VESA) Local (VL) bus standard allows high-speed connections to peripheral devices. VL bus devices are not completely Plug and Play but work similarly to ISA devices.

PCI Devices

The peripheral component interconnect (PCI) local bus meets most Plug and Play requirements. It is considered the successor to the VL bus. The PCI bus and devices use agreed-upon mechanisms for identifying themselves and declaring their resource settings and requirements. Windows gathers PCI and ISA Plug and Play device resource information from the system BIOS, which provides the PCI IRQ Steering Table for PCI devices. With the information from the PCI IRQ Steering Table, Windows 2000 Professional can reassign PCI device resource requirements dynamically, if necessary. For example, when a PCI-based portable computer is hot-docked into a docking station, Windows 2000 Professional might dynamically reassign a PCI devices IRQ to accommodate the new hardware.

Note

Windows 2000 Professional can manipulate only the physical IRQ that is mapped to a particular PCI INT#. It cannot alter the link value for the PCI device listed in the PCI IRQ Routing Table. (The link value is the combination of the devices INT# assignment and the specific PCI slot the device is installed in.)

ISA Devices

Industry Standard Architecture (ISA) bus design is the architecture specified for the IBM PC/AT. Plug and Play ISA devices can be used on existing computers, because the specification does not require any change to ISA buses. To configure Plug and Play ISA devices, the system performs the following actions:

• Isolates each card and retrieves a unique device ID and a unique serial number.

• Reads the resource requirements and capabilities stored on each card.

• Allocates resources to each card, reserving these resources so that they cannot be assigned to other Plug and Play cards in the computer.

• Activates the Plug and Play ISA cards.

For legacy devices, standard ISA cards can coexist with Plug and Play ISA cards in the same computer. Windows 2000 Professional determines the type of hardware and its configuration during Setup, by either polling the hardware or asking the user to supply values. This configuration information is stored as static values in the registry and cannot be changed dynamically, but it is used to determine resource assignments for Plug and Play devices.

EISA Devices

Extended Industry Standard Architecture (EISA) is a bus design specified by an industry consortium. EISA devices use cards that are upwardly compatible from ISA and standard software mechanisms for identification and configuration. Windows 2000 Professional includes a bus enumerator that makes configuration information from these devices accessible to the operating system. Windows 2000 Professional does not reconfigure EISA cards, but it uses the information that hardware detection derives from the EISA nonvolatile RAM storage to determine which resources are used.

Other Device Types

Other device types can take advantage of Plug and Play if they provide mechanisms for identification and configuration. These include integrated device electronics (IDE) controllers, Extended Capabilities Ports (ECPs), and communications ports.

Parallel ports can also take advantage of Plug and Play. The most common parallel port type is the Centronics interface. Plug and Play parallel ports meet Compatibility and Nibble mode protocols defined in IEEE P1284. Compatibility mode provides a byte-wide channel from the computer to the peripheral. Nibble mode provides a channel from the peripheral to the host through which data is sent as 4-bit nibbles using the ports status lines. These modes provide two-way communication between the host and the peripheral. Nibble mode is also used to read the device ID from the peripheral for device enumeration.

For totally Plug and Play–compliant computers, the BIOS must also meet Plug and Play specifications.

With Plug and Play, the operating system and the BIOS can communicate with each other to share information about system resources. This communication channel is not new, but with newer system BIOSs combined with either Windows 2000 Professional or Windows 98, this process is more effective than with previous Plug and Play implementations.